U.S. patent number 7,151,532 [Application Number 10/216,507] was granted by the patent office on 2006-12-19 for multifunctional multilayer optical film.
This patent grant is currently assigned to 3M Innovative Properties Company. Invention is credited to Stephen C. Schulz.
United States Patent |
7,151,532 |
Schulz |
December 19, 2006 |
Multifunctional multilayer optical film
Abstract
Optical component for use in a touch sensor and method of
fabrication of same are disclosed. Optical component includes a
multilayer optical film at least some layers of which are
fabricated on the same manufacturing line and using the same
manufacturing method. Each layer of the multilayer optical film is
designed primarily to provide a desired associated property.
Inventors: |
Schulz; Stephen C. (Lee,
NH) |
Assignee: |
3M Innovative Properties
Company (St. Paul, MN)
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Family
ID: |
31495075 |
Appl.
No.: |
10/216,507 |
Filed: |
August 9, 2002 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20040027339 A1 |
Feb 12, 2004 |
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Current U.S.
Class: |
345/173;
345/179 |
Current CPC
Class: |
G06F
3/045 (20130101); C03C 17/3435 (20130101); C03C
17/3417 (20130101); G06F 3/0445 (20190501) |
Current International
Class: |
G09G
5/00 (20060101) |
Field of
Search: |
;345/173-178,179
;427/164-167,255 ;428/426-428 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1 172 831 |
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Jan 2002 |
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EP |
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2355273 |
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Apr 2001 |
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GB |
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07-315880 |
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Dec 1995 |
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JP |
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07315880 |
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Dec 1995 |
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JP |
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08-138446 |
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May 1996 |
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JP |
|
08138446 |
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May 1996 |
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JP |
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0229830 |
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Apr 2002 |
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WO |
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Primary Examiner: Hjerpe; Richard
Assistant Examiner: Lesperance; Jean
Attorney, Agent or Firm: Pechman; Robert J.
Claims
What is claimed is:
1. A capacitive touch sensor comprising: a glass substrate; a
transparent conductive film disposed on the substrate and
configured for detecting a touch by capacitively coupling to a
conductive touch object; a barrier film disposed between the
substrate and the transparent conductive film and configured to
isolate the transparent conductive film from impurities present in
the glass substrate; an antiglare coating disposed over the
transparent conductive film; and electrical leads connecting the
transparent conductive film to electronic circuitry for determining
location of the touch.
2. The capacitive touch sensor of claim 1, further comprising an
antireflective film disposed between the transparent conductive
film and the antiglare coating.
3. The capacitive touch sensor of claim 1, wherein the glass
substrate is a float glass substrate.
4. The capacitive touch sensor of claim 1, wherein the antiglare
coating incorporates particles.
5. The capacitive touch sensor of claim 1, wherein the antiglare
coating is formed by spraying.
6. The capacitive touch sensor of claim 1, wherein the antiglare
coating comprises silicon dioxide.
7. The capacitive touch sensor of claim 1, wherein the transparent
conductive film comprises indium tin oxide.
8. The capacitive touch sensor of claim 1, wherein the transparent
conductive film comprises fluorine doped tin oxide.
9. The capacitive touch sensor of claim 1, wherein the transparent
conductive film comprises antimony tin oxide.
10. The capacitive touch sensor of claim 1, wherein the transparent
conductive film comprises zinc oxide.
11. The capacitive touch sensor of claim 1, wherein the barrier
film comprises silicon dioxide.
12. The capacitive touch sensor of claim 1, wherein the barrier
film comprises tin oxide.
13. The capacitive touch sensor of claim 1, further comprising an
abrasion resistant film for resisting abrasion to the capacitive
touch sensor due to repeated touch inputs.
Description
FIELD OF THE INVENTION
This invention generally relates to touch sensing devices. The
invention is particularly applicable to such devices used in
electronic display systems.
BACKGROUND
Touch screens allow a user to conveniently interface with an
electronic display system by reducing or eliminating the need for a
keyboard. For example, a user can carry out a complicated sequence
of instructions by simply touching the screen at a location
identified by a pre-programmed icon. The on-screen menu may be
changed by re-programming the supporting software according to the
application.
Resistive and capacitive are two common touch sensing technologies.
Both technologies typically incorporate one or more transparent
conductive films as part of an electronic circuit that detects the
location of a touch.
The performance of a touch screen is described in terms of various
characteristics of the screen. One such characteristic is optical
transmission. Image brightness and contrast increase as a touch
screen's optical transmission is improved. High optical
transmission is particularly desired in portable devices where the
display is often powered by a battery with limited lifetime.
Optical transmission may be optimized by improving optical clarity
of different layers in the touch screen, and by reducing reflection
at various interfaces. Typically, anti-reflection coatings are used
to reduce reflection losses.
Another characteristic of a touch screen is the amount of glare.
Polished surfaces in a touch screen specularly reflect ambient
light towards a viewer. Such specular reflection is generally
referred to as glare and will reduce the viewability of the
displayed information. Glare from a polished surface is typically
reduced by making the surface optically diffusive. Such diffuse
surface is sometimes referred to as a matte or rough surface. Glare
may also be reduced by coating the polished surface with a film
having a matte or rough surface. Such coating is sometimes referred
to as an anti-glare coating.
Another characteristic of a touch screen is durability. Generally,
touch screens are susceptible to physical damage such as
scratching. A user may use a stylus, finger, pen, or any other
convenient touch implement to apply a touch. The ability of a touch
screen to resist scratching affects screen durability, and hence,
screen lifetime. Typically, a touch screen's durability is improved
by coating surfaces that are susceptible to scratching with a
scratch-resistant film. Such a film is sometimes referred to as an
abrasion resistant film.
Another characteristic of a touch screen is overall cost.
Generally, manufacturing cost increases as the number of layers in
a touch screen is increased. As one screen characteristic is
improved, one or more other characteristics often degrade. For
example, in an attempt to reduce manufacturing cost, the number of
layers in a touch screen may be reduced, hence, compromising other
properties of the touch screen such as durability, optical
transmission, or contrast. As a result, certain tradeoffs are made
in a touch screen in order to best meet the performance criteria
for a given application. Therefore, there remains a need for touch
screens with improved overall performance.
SUMMARY OF THE INVENTION
Generally, the present invention relates to touch sensors and touch
sensing displays where it is desirable to have a set of desired
properties with no or little trade off and where it is further
desirable to reduce manufacturing cost.
In one aspect of the invention a method of manufacturing a touch
sensor component includes manufacturing a glass substrate followed
by using atmospheric pressure chemical vapor deposition to deposit
at least four films onto the glass substrate where the first film
is designed primarily to have a desired optical clarity and sheet
resistance, the second film is designed primarily to isolate the
first film from the substrate, the third film is designed primarily
to resist abrasion, and the fourth film is designed primarily to
reduce glare.
In another aspect of the invention a method of manufacturing an
optical component for use in a touch sensor includes using the same
deposition technique to form a multilayer optical film onto a glass
substrate all fabricated on the same manufacturing line where the
multilayer optical film includes a first film designed primarily to
have a desired optical clarity and sheet resistance, a second film
is designed primarily to isolate the first film from the substrate,
and a third film is designed primarily to provide a desired
resistance to abrasion.
In another aspect of the invention a method of manufacturing a
multilayer optical film for use in a touch sensor includes forming
a glass substrate on a manufacturing line, and on the same
manufacturing line and using the same film deposition technique to
deposit a transparent conductive film primarily designed to provide
a desired optical transmission and sheet resistance, and a barrier
film designed primarily to isolate the conductive film from the
substrate.
In another aspect of the invention an optical component for use in
a touch sensor includes a substrate manufactured using a float
technology, and at least three films formed onto the substrate
using the same technology where at least a first film is designed
primarily to provide a desired optical clarity and conductivity, at
least a second film is designed primarily to isolate the first film
from the substrate, and at least a third film is designed primarily
to provide resistance to abrasion.
In another aspect of the invention a touch sensitive display
includes a float glass substrate and at least four films formed
onto the glass substrate using an atmospheric pressure chemical
vapor deposition technique where the first film is designed
primarily for a pre-determined optical clarity and electrical
conductivity, the second film is designed primarily for isolating
the first film from the substrate, the third film is designed
primarily for resisting abrasion, and the fourth film is designed
primarily to reduce glare.
BRIEF DESCRIPTION OF DRAWINGS
The invention may be more completely understood and appreciated in
consideration of the following detailed description of various
embodiments of the invention in connection with the accompanying
drawings, in which:
FIG. 1 illustrates a schematic side view of an optical component in
accordance with an embodiment of the invention;
FIG. 2 illustrates a schematic three dimensional view of a touch
sensor in accordance with another embodiment of the invention;
FIG. 3 illustrates a schematic side view of an optical component in
accordance with another embodiment of the invention;
FIG. 4 illustrates a schematic side view of an optical component in
accordance with yet another embodiment of the invention;
FIG. 5 illustrates a schematic three dimensional view of a touch
sensor in accordance with another embodiment of the invention;
FIG. 6 illustrates a schematic side view of an optical component in
accordance with another embodiment of the invention;
FIG. 7 illustrates a schematic side view of a display system in
accordance with another embodiment of the invention; and
FIGS. 8A 8D illustrate schematic side views of four optical
components in accordance with other embodiments of the
invention.
DETAILED DESCRIPTION
The present invention is generally applicable to touch screens,
touch screens used with electronic display systems, and
particularly where it is desirable for a touch screen to have high
optical transmission, high contrast, high durability, low glare,
low reflection, and low manufacturing cost. The present invention
allows the optimization of a touch screen's desirable properties
with no or little trade off. The present invention, furthermore,
describes implementation of some of the listed desirable properties
into a single layer, thereby further reducing design and
manufacturing costs.
A touch screen can work on the general principle that an otherwise
open electrical circuit is closed when a touch is applied. The
properties of a signal generated in the closed circuit allows
detection of a touch location. Different technologies may be
employed to detect a touch location. One such technology is
resistive. In a resistive touch, an applied touch brings two
otherwise physically separated conductive films into direct
physical contact with one another. The physical contact closes an
otherwise open electronic circuit, thereby resulting in generation
of a resistively coupled electrical signal. The properties of the
generated signal allow detection of the touch location.
Capacitive is another technology commonly used to detect the
location of a touch. In this case, a signal is generated when a
conductive touch applicator, such as a user's finger, is brought
sufficiently close to a conductive film to allow capacitive
coupling between the two conductors. The two conductors are
electrically connected to each other, for example, through the
earth ground. Properties of the generated signal allow detection of
the touch location. Other viable technologies include surface
acoustic wave, infrared, and force.
The present invention is applicable to touch sensing screens where
it is desirable for a touch screen to be scratch resistant, have
low glare, low reflection, high optical transmission, and low
manufacturing cost. The present invention is particularly
applicable to touch screens utilizing resistive or capacitive
technologies to detect the location of a touch. For example, one
embodiment of the present invention is well suited for use in a
capacitive touch screen where it is desirable to have optimized
abrasion resistance and anti-reflection properties with reduced
manufacturing cost. Another embodiment of the present invention is
particularly suitable for use in a resistive touch screen where it
is desirable for the conductive sheets to have optically diffuse
surfaces with reduced manufacturing cost.
According to the present invention the overall performance of a
touch sensor can be improved by designing each layer primarily to
provide a particular characteristic of the touch sensor at a
desired level. For example, a given layer in the touch sensor can
be designed primarily to provide a pre-determined optical
transmission and sheet resistance. A different layer can be
designed primarily to provide a pre-determined minimum resistance
to abrasion, and yet a different layer can be designed principally
to reduce glare.
According to the present invention, where two or more desired
characteristics in a touch sensor can not at the same time be
effectively provided for by designing a single, multifunctional
layer, each characteristic is provided for by designing a separate
layer dedicated primarily to providing that characteristic at a
pre-determined level. For example, a conventional capacitive touch
sensor typically incorporates an abrasion resistant film to protect
a transparent conductive sheet from damage due to repeated touches.
Typically the same film is also designed to reduce reflection.
However, the optimum design values for the two characteristics of
resistance to abrasion and reduced reflection typically require a
compromise in one or both characteristics. For example, effective
abrasion resistant materials tend to have a higher index of
refraction than materials used to reduce reflection. In addition, a
design to provide resistance to abrasion typically requires a film
thickness that can be substantially different than a design that
effectively reduces reflection. As a result, it is difficult for a
single film to simultaneously provide sufficient resistance to
abrasion and reduction in reflection. According to the present
invention, a first layer can be designed primarily to provide
sufficient abrasion resistance and a second layer can be designed
primarily to reduce glare. The two layers can have different
indices of refraction, thickness, and material composition.
According to the present invention, the potential increase in
manufacturing cost due to an increase in the number of layers can
be mitigated by sequentially depositing at least some of the
constituent layers on the same manufacturing line. For example, the
coatings can be applied to a glass substrate during the glass
manufacturing process. For example, the coatings can be applied to
a hot float glass in or subsequent to the float bath. U.S. Pat.
Nos. 6,106,892 and 6,248,397 disclose deposition of a silicon oxide
coating on hot glass. U.S. Pat. No. 5,773,086 discloses deposition
of an indium oxide coating to the surface of a hot glass. In one
particular embodiment of the present invention, a multilayer
optical component is manufactured that includes the following
steps. First, a glass substrate is manufactured on a float bath.
Second, while on the bath or after removing the glass substrate
from the bath a barrier layer of silicon dioxide or tin oxide is
deposited onto the hot glass substrate using atmospheric pressure
chemical vapor deposition (APCVD). Next, a layer of transparent
conductor such as a fluorine doped tin oxide is deposited onto the
barrier layer. The transparent conductor is primarily designed to
have a pre-determined optical clarity and sheet resistance. The
barrier layer is designed primarily to isolate the transparent
conductor from the float glass. Finally, an anti-reflective film
coating is deposited onto the transparent conductor film using
APCVD, where the anti-reflective film coating is designed primarily
to reduce reflection to a desired level. It will be appreciated
that additional layers can be deposited on the same or a different
manufacturing line using APCVD or a different manufacturing
technique to provide additional functionalities.
FIG. 1 illustrates a schematic cross-section of a multilayer
optical film 100 in accordance with one particular embodiment of
the present invention. Optical film 100 is a component suitable,
for example, for use in a touch sensor. Optical film 100 includes a
substrate 101, a transparent conducting film 102, an abrasion
resistant film 103, and an anti-reflection film 104. Substrate 101
may be flexible or rigid. Substrate 101 is preferably highly
optically transmissive. Transparent conductive film 102 is designed
primarily to provide a desired optical clarity, sheet resistance,
and sheet resistance uniformity. Abrasion resistant film 103 is
designed primarily to provide optimum protection against abrasion.
Anti-reflective film 104 is designed primarily to reduce reflection
to a desired level by using light interference. The different films
in optical film 100 may each be a single layer or multiple layers.
For example, anti-reflective film 104 may include one or more
layers of high and low indices of refraction. Suitable materials
for anti-reflective film 104 include materials having a low index
of refraction, for example, in the range of 1.35 to 1.5, although
in some applications other indices of refraction can be used. In
addition, the optical thickness of each layer in the
anti-reflective film film, where the optical thickness is defined
as the product of the physical thickness and index of refraction of
the layer, is typically close to a quarter of a wave, for example,
in the 50 to 150 nanometer range, although thinner or thicker films
can also be used depending on the application. Materials
particularly suitable for abrasion resistant film 103 typically
have a high index of refraction, for example, in the range of 1.6
to 2.7, although in some applications other indices of refraction
can be used. In addition, in order to provide adequate resistance
to abrasion, the abrasion resistant film should be sufficiently
thick, and a sufficient thickness may or may not be much larger
than a quarter wave.
To reduce manufacturing cost, it is common in known constructions
for a single film to be designed to provide two or more properties.
As discussed above, however, this approach often requires
conflicting design parameters which can result in reduced
performance. For example, if in the optical film 100 of FIG. 1 a
single film is designed to provide the properties of resistance to
abrasion and reduced reflection, the potential conflicting
requirements of material composition, index of refraction, and
thickness often result in a compromise in one or both properties.
More specifically, for example, the thickness of abrasion resistant
film 103, designed primarily to provide sufficient abrasion, may
have to be larger than the thickness of anti-reflective film 104,
designed primarily to reduce reflection to a desired level. In
addition, the index of refraction of abrasion resistant film 103 is
typically larger than that of the anti-reflective film 104.
Therefore, if a single film was designed to provide anti-abrasion
and anti-reflection properties, a compromise would need to be made.
The present invention alleviates the need for this compromise by
designing abrasion resistant film 103 primarily to provide a
desired resistance to abrasion, and anti-reflective film 104
primarily to reduce reflection. Therefore, in the present
invention, each of these properties are independently provided by
separate films, each of which is designed primarily to provide a
specific property to the desired level without particular concern
for the compromise that is often required when attempting to
provide multiple functionalities in fewer layers.
While each of the films described in the present invention is
primarily responsible for providing its associated properties in an
overall construction, the films may contribute to properties for
which they were not primarily designed. For example, the abrasion
resistant film may contribute to reducing reflection even though
the antireflective film is designed to be the primary provider of
anti-reflection functionality.
As another example, the thickness of transparent conductive film
102, designed primarily to provide optical clarity and
conductivity, is generally different than the thickness of
anti-reflective film 104 designed primarily to reduce reflection.
To reduce manufacturing cost, in known constructions a single film
is typically designed to provide properties of conductivity and
reduced reflection. However, since each property generally requires
a different thickness, at least one of the two properties remains
at an undesired level. The present invention allows optimization of
both properties by designing a separate film 102 to provide a
desired clarity and conductivity, and another film 104 to minimize
reflection.
As discussed, manufacturing cost of optical film 100 can be reduced
by coating most or all the films in optical film 100 on the same
suitable manufacturing line. Exemplary manufacturing methods
include chemical vapor deposition (CVD), APCVD, vacuum deposition
(such as evaporation or sputtering), solvent-based coating, cast
and cure, and other similar coating techniques.
APCVD is particularly advantageous when substrate 101 is made of
glass. In this case, layers 102, 103, and 104 can be coated on the
same general line where the glass substrate is manufactured,
thereby reducing cost. The layers can be sequentially deposited,
for example at different coating stations, at elevated temperatures
on a hot glass substrate. Deposition at elevated temperatures and
on a hot substrate can be particularly advantageous because such
conditions tend to improve optical, electrical, and durability
properties of the deposited films. Durability includes mechanical,
processing, and environmental durability. Alternatively, films 102
and 103 can be deposited using APCVD and layer 104 can be deposited
using a different method such as vacuum deposition.
Vacuum deposition, such as sputtering, may be used to deposit
layers 102, 103, and 104. Substrate 101 may be flexible or rigid.
For example, substrate 101 may be in the form of a roll of a
polymeric material. In this case, layers 102, 103, and 104 may be
coated sequentially on a web line.
Alternatively, the different layers of optical film 100 can be
solvent coated or cast and cured. For example, the layers may be
roll coated on a roll of flexible polymeric substrate. Such method
is particularly advantageous where transparent conductive film is a
transparent organic conductor. In this case, layers 102, 103, and
104 may be sequentially coated and dried/cured on substrate
101.
Optical film 100 is suitable for use in touch sensors and is
particularly suitable for use in a capacitive touch sensor. Optical
film 100 provides means by which high optical transmission, low
reflection, high abrasion resistance, and optimum sheet resistance
can be achieved with no or little trade-off. It will be appreciated
that while a given layer in optical film 100 is designed primarily
to optimize a given property, one or more secondary properties may
also be optimized without compromising the primary properties.
Optimization of such secondary properties can be by design or
incidental or consequential to the primary objective. For example,
in a given application where transparent conductive film 102 is
designed primarily to provide clarity and optical conductivity, the
thickness of layer 102 can be such that the layer also reduces
interfacial reflections. As another example, in an application
where abrasion resistant film 103 is designed primarily to provide
sufficient abrasion, the film thickness can be such that the film
also reduces reflection without compromising the primary intended
property of resistance to abrasion.
Optical film 100 may further include anti-glare properties by
optically diffusing a reflected light. Four such exemplary
embodiments according to different aspects of the present invention
are shown in FIGS. 8A 8D. Optical film 800A in FIG. 8A includes a
substrate 801A with a substantially smooth surface 801A', a
transparent conductive film 802A with a substantially smooth
surface 802A', an abrasion resistant film 803A with a substantially
smooth surface 803A', an anti-reflective film 804A with a
substantially smooth surface 804A', and an anti-glare film
(anti-glare film) 805A with a diffuse surface 805A'. Layers 801A
804A are similar to the layers in optical film 100 described in
reference to FIG. 1.
Anti-glare film 805A is designed primarily to reduce specular
reflection to a desired level for a particular application, for
example, by diffusing the reflected light. According to FIG. 8A,
anti-glare film 805A reduces glare by virtue of a matte surface
805A'. anti-glare film 805A may further include bulk diffusion
properties, for example, by incorporating particles having an index
of refraction different than their surrounding material. Matte
surface 805A' may be generated in a number of ways. For example,
the surface may be generating by embossing layer 805A against a
matte tool. Alternatively, the matte surface may be generated by
appropriately choosing deposition parameters as film 805A is
deposited. For example, where anti-glare film 805A is solvent
coated, drying conditions can be chosen to result in a matte
surface 805A' upon drying. Alternatively, anti-glare film 805A can
be coated using vacuum deposition, CVD, or APCVD in such a way that
the resulting film has a matte surface. Alternatively, anti-glare
film 805A can include a coating of particles dispersed in a host
material, where the particles impart a matte surface to the film
by, for example, partially protruding through the host material. As
yet another example, matte surface 805A' may be generated by
casting and curing film 805A against a textured tool.
Alternatively, anti-glare film 805A can be constructed by spraying
a material such a sol gel, for example, in the form of droplets,
onto film 804A. The sprayed material can be the same as that of
film 804A.
According to FIG. 8A, optical film 800A has anti-glare properties
by virtue of an additional film 805A. Alternatively, an anti-glare
property can be achieved by roughening surface of anti-reflective
film 104 of FIG. 1. This is shown in FIG. 8B. Optical film 800B in
FIG. 8B includes a substrate 801B with a substantially smooth
surface 801 B', a transparent conductive film 802B with a
substantially smooth surface 802B', an abrasion resistant film 803B
with a substantially smooth surface 803B', and an anti-reflective
film 804B with a matte surface 804B'. Layers 801B 803B are
analogous to the layers in optical film 100 described in reference
to FIG. 1. In this construction anti-reflective film 804B which is
designed primarily to reduce reflection has the added anti-glare
property because of surface 804B'. The anti-glare property is
achieved with little or no compromise in the primary objective of
film 804B.
FIG. 8C illustrates another embodiment of the present invention.
Optical film 800C in FIG. 8C includes a substrate 801C with a
substantially smooth surface 801C', a transparent conductive film
802C with a substantially smooth surface 802C', an abrasion
resistant film 803C with a matte surface 803B', and an
anti-reflective film 804C with a matte surface 804C'. Layers 801C
802C are analogous to the layers in optical film 100 described in
reference to FIG. 1. In optical film 800C, abrasion resistant film
803C is designed primarily to provide sufficient abrasion
resistance abrasion resistant film 803C also has a matte surface
803C'. When anti-reflective film film 804C is substantially
conformally coated onto layer 803C, a matte surface 804C' is
created which provides anti-glare properties for optical film 800C.
This construction is particularly suitable, for example, where it
is easier or more advantageous to generate a matte finish directly
in layer 803C than in layer 804C. In optical film 800C, a matte
surface is generated directly in layer 803C and indirectly in layer
804C by a substantially conformal coating of layer 804C onto layer
803C.
FIG. 8D shows an optical film 800D according to yet another aspect
of the present invention. Optical film 800D includes a substrate
801D with a matte surface 801D', a transparent conductive film 802D
with a matte surface 802D', an abrasion resistant film 803D with a
matte surface 803D', and an anti-reflective film 804D with a matte
surface 804D'. In optical film 800D, first a matte surface 801D' is
generated directly in substrate 801D. For example, matte surface
801D' can be generated during the manufacturing of substrate 801 D.
Next, layers 802D 804D (similar to layers 802C 804C) are
sequentially and substantially conformally coated resulting in a
matte surface 804D' in the anti-reflection layer 804D. For example,
where substrate 801D is glass, surface 801D' may be generated using
chemical etching. Alternatively, surface 801D' can be generated
when the glass substrate is manufactured, for example, by forming
the glass against a textured tool. Next, all the other layers may
be sequentially and conformally coated, at elevated temperatures,
on the hot glass substrate by, for example, using an APCVD method.
Hence, using APCVD, optical film 800D can be manufactured with low
cost and with desired optical transmission, reflection, glare,
abrasion resistance, and electrical-conductivity.
It will be appreciated that the sequence or order of the different
layers in FIG. 8 may be changed according to application. For
example, in FIG. 8D, abrasion resistant film 803D may be deposited
on substrate 801D before depositing transparent conductive film
802D.
FIG. 2 schematically illustrates a capacitive touch sensor 200 in
accordance with an embodiment of the present invention. Capacitive
touch sensor 200 includes a touch panel 210, electrical leads 205,
206, 207, 208, and electronic circuitry 209. Touch panel 210
includes a substrate 201, a transparent conductive film 202, an
abrasion resistant film 203, and an anti-reflective film 204. The
layers in touch panel 210 are similar to those described in
reference to optical film 100 of FIG. 1. Touch panel 210 is a
capacitive touch panel. Electrical leads 205, 206, 207, and 208
electrically connect the four corners of transparent conductive
film 202 to electronic circuitry 209. Electronic circuitry 209
includes electronics and software for determining a location of a
touch and processing the collected information as desired in a
given application. Electronic circuitry 209 further includes
software for providing an application dependant user menu and for
processing information. As an example, when a user applies a finger
touch to touch panel 210 at location X, current flows through the
four corners of transparent conductive film 202. This current
capacitively couples to the user's finger or other conductive touch
implement. Electronic circuitry 209 then determines the location of
the touch by comparing the relative magnitudes of currents flowing
through the four leads connected to the four corners of transparent
conductive film 202.
Touch panel 210 can also include a pattern of resistors to
linearize the electrical field across the panel, which pattern is
not shown in FIG. 2 for simplicity and without any loss of
generality. One such linearization method is described in U.S. Pat.
No. 4,371,746.
Touch panel 210 can provide increased transmission, reduced
reflection, and optimized abrasion resistance with no or little
trade off. Substrate 201 is preferably optically transmissive and
is designed to provide mechanical rigidity or flexibility as
required in an application. Transparent conductive film 202 is
designed to primarily provide optical clarity and a desired sheet
resistance. Abrasion resistant film 203 is designed to primarily
make touch panel 210 resistant to abrasion. Such abrasion may
occur, for example, when a user touches the panel with a hard or
rough stylus, or with repeated touches. Abrasion resistance is
important to protect the transparent conducting film 202, and to
maintain optical, electrical, and cosmetic properties of touch
panel 210 during its expected lifetime. Anti-reflective film 204 is
designed to primarily reduce reflection, thereby reducing glare and
increasing contrast. Anti-reflective film 204 may be a single layer
or a multilayer. Each layer in anti-reflective film 204 typically
has a pre-determined optical thickness, for example, close to a
quarter of a wavelength, for example, in the visible region. Each
layer may further be organic or inorganic. It will be appreciated
that according to the present invention, properties of touch panel
210 such as optical transmission, sheet resistance, abrasion
resistance, and reduced reflection can each be independently tuned
to a desired level with no or little need for a trade off. It will
further be appreciated that touch panel 210 in FIG. 2 can be
constructed analogously to the embodiments described in reference
to FIGS. 8A 8D or any other suitable embodiment with accordance to
the present invention.
FIG. 3 illustrates a schematic cross-section of an optical film 300
in accordance with another embodiment of the present invention.
Optical film 300 includes a substrate 301, a transparent conductive
film 303 designed primarily to provide optical clarity and
electrical conductivity, an abrasion resistant film 304 designed to
primarily provide anti-abrasion properties, an anti-reflective film
305 designed to primarily reduce reflection, and an anti-glare film
306 designed primarily to reduce or eliminate glare. Optical film
300 further includes a barrier film 302 designed to primarily
isolate transparent conductive film 303 from substrate 301. Such
isolation can be desired to reduce or eliminate potential undesired
interactions between substrate 301 and transparent conductive film
303. One such interaction may be chemical reaction between
substrate 301 and transparent conductive film 303 that may
adversely affect, for example, optical and/or electrical properties
of transparent conductive film 303. As another example, substrate
301 may include particles or impurities which, in the absence of
barrier film 302, could migrate into transparent conductive film
303, thereby adversely affect electrical and/or optical properties
of transparent conductive film 303. Such migration may occur during
processing and manufacturing of optical film 300, during assembly,
during use, or for other reasons. Barrier film 302 stops or reduces
such migration. For example, substrate 301 may be glass having
impurities such as sodium, and transparent conductive film 303 may
be a transparent conductive oxide (TCO). Examples of a TCO include
indium tin oxide (ITO), fluorine doped tin oxide, antimony tin
oxide (ATO), and zinc oxide (ZnO), for example, doped with
aluminum. In the absence of barrier film 302, impurities in the
glass can migrate into the TCO, thereby increasing its sheet
resistance and/or reducing its optical clarity. Such migration may,
for example, occur at elevated temperatures over a short time, or
at lower temperatures over a longer time period. For example, a TCO
is typically deposited at elevated temperatures, for example,
150.degree. C. or more. At such temperatures impurities can migrate
from the substrate into the deposited TCO film, thereby reducing
its conductivity and/or optical clarity. Furthermore, electrical
and optical properties of a TCO film can be improved if the film is
baked at an elevated temperature subsequent to deposition of the
film. The post deposition bake is sometimes referred to as
annealing. In the absence of a barrier film, impurities may migrate
from the substrate into a TCO film during annealing even if the TCO
film was initially deposited at low temperatures. In the absence of
barrier film 302, it may be desirable for substrate 301 to be
substantially free of impurities. Impurity free substrates limit
the choice of substrate and increase the cost. Adding barrier film
303 allows use of glass with impurities, such as float glass.
Anti-glare film 306 is primarily designed to diffuse residual
reflection, thereby further reducing or eliminating glare.
Anti-glare film 306 may have anti-glare properties by virtue of
having a rough surface 307. Such rough surface may be generated
while depositing anti-glare film 306, for example, by optimizing
coating and drying conditions. Surface 307 may also be generated
using other methods including embossing, microreplication,
spraying, or other methods. Alternatively, anti-glare film 307 may
include a bulk diffuser that imparts a textured surface to the
film. It will be appreciated that, alternatively, optical film 300
can have anti-glare properties by incorporating a construction
similar to those described in reference to FIGS. 8A 8D.
It will further be appreciated that optical film 300 provides
desired optical transmission, sheet conductivity, reflection,
glare, and abrasion resistance with no or little trade off.
Furthermore, optical film 300 allows high temperature processing,
for example, in vacuum or in close to atmospheric pressure
environment, by virtue of isolating transparent conductive film 303
from substrate 301. In addition, one or more of layers 304 306 can
contribute to protecting the transparent conducting film 303 from
undesired effects such as oxidation, impurities that may exist in
air, and other potentially undesired effects during further
processing. Optical film 300 is suitable for use in a touch sensor.
For example, the optical film may be used in a capacitive touch
sensor similar to the circuit shown in FIG. 2.
FIG. 4 describes a schematic cross-section of an optical film 400
in accordance with another embodiment of the present invention.
Optical film 400 includes a substrate 410, a transparent conductive
film 403 designed primarily to provide optical clarity and
electrical conductivity, and a barrier film 402 designed primarily
to isolate substrate 401 from transparent conductive film 403. The
different layers in optical film 400 are similar to those described
in the embodiment described in reference to FIG. 3. Transparent
conductive film 403 has a textured surface 404 to reduce glare.
Hence, in this particular embodiment of the present invention the
transparent conductive film has the secondary anti-glare property
without compromising the primary properties of optical clarity and
sheet conductivity. Textured surface 404 can be created during
deposition of transparent conductive film 403. For example, in a
vacuum deposition of transparent conductive film 403, the
deposition parameters may be chosen to result in a final rough
surface 404. Alternatively, the surface can be roughened by a
post-deposition dry or wet chemical or mechanical etch.
Alternatively, (CVD) or (APCVD) can be used to deposit transparent
conductive film 403 with a finished rough surface 404. For example,
barrier film 403 can be deposited, using APCVD, on a hot glass
substrate 401. Next, transparent conductive film 403 can be
deposited, using APCVD, on a hot barrier film 402 and substrate
401. It will be appreciated that each film in FIG. 4 can include
more than one layer.
As discussed previously, a particular advantage of APCVD is that
most or all layers of optical film 400 can be deposited at
atmospheric pressure and at elevated temperatures. Such processing
conditions generally reduce cost and improve optical and electrical
performance. Furthermore, layers can be coated sequentially on the
same manufacturing line to further reduce cost. Another particular
advantage of APCVD is that the layers can be coated on the same
line the glass substrate 401 is produced, thereby further reducing
cost. Barrier film 402 reduces or eliminates migration of
impurities from substrate 401 to transparent conductive film 403.
Thus, inexpensive glass with impurities may be used to produce the
glass substrate. Barrier film 402, by blocking migration of
impurities from the substrate, allows deposition of transparent
conductive film 403 at elevated temperatures without compromising
optical and electrical properties of the conductor. It will be
appreciated that, according to the present invention, optical film
400 may have other layers such as an abrasion resistant film
designed primarily to increase resistance of optical film 400 to
abrasion. It will further be appreciated that, similar to the
discussion in reference to FIG. 8, matte surface 404 may be
generated directly in transparent conductive film 403, or
indirectly, by for example, first generating a matte surface
directly in barrier film 402, and then substantially conformally
coating a transparent conducting film onto barrier film 402
resulting in a matte surface 404.
FIG. 5 illustrates a schematic of a resistive touch sensor 500 in
accordance with another aspect of the present invention. Resistive
touch panel 500 includes a top sheet 530 and a bottom sheet 540.
Top sheet 530 includes a transparent conductor 511 that faces the
bottom sheet. Electrodes 505 make electrical contact with
transparent conductor 511. Bottom sheet 540 includes a substrate
501, a transparent conductive film 503 designed primarily to
provide optical clarity and sheet conductivity, and a barrier film
502 designed primarily to isolate substrate 501 from transparent
conductive film 503. The top surface of transparent conductive film
503 (surface 504) can be rough or textured. Electrodes 506 are in
electrical contact with transparent conductive film 503. Leads 507
and 508 connect top transparent conductor 511 and bottom
transparent conductor 503 to electronic circuitry 510.
An applied touch brings top and bottom transparent conductors, 511
and 503, into physical contact with one another at the location of
touch. Touch location is determined by first energizing electrodes
505 and using conductor 503 to determine the y-coordinate of the
touch location. Next, electrodes 506 are energized and top sheet
conductor 511 is used to determine the x-coordinate of the touch
location.
Bottom sheet 540 provides a desired optical clarity and sheet
conductivity. The roughened surface 504 reduces or eliminates
glare. In addition, matte surface 504 reduces or eliminates optical
interference between top and bottom sheets, especially at or near a
location of a touch. Such an optical interference is sometimes
referred to as Newton's rings and is, generally, apparent to a
viewer. Newton's rings are generally undesirable because they
reduce contrast and interfere with easy viewing of information
displayed through touch sensor 500. Roughened surface 504 reduces
Newton's rings to an acceptable level or eliminates them. It will
be appreciated that, according to the present invention, touch
sensor 500 provides desired optical clarity, glare, substantially
invisible Newton's rings, desired sheet resistance, and reduced
manufacturing cost with little or no trade off.
FIG. 6 illustrates a schematic cross-section of an optical film 600
in accordance with another embodiment of the present invention.
Optical film 600 includes a substrate 601 with a rough top surface
604, a barrier film 602 with a rough top surface 605, and a
transparent conductive film 603 with a rough top surface 606.
Transparent conductive film 603 is designed primarily to provide
optimum optical clarity and sheet conductivity. Transparent
conductive film 603 also has a secondary antiglare property by
virtue of matte surface 606. Barrier film 602 is designed primarily
to isolated transparent conductive film 603 from substrate 601, and
has a secondary antiglare property. Glare in optical film 600 is
reduced or eliminated by virtue of diffuse surfaces 604, 605, and
606. Optical film 600 is suitable for use in a touch sensor and
provides desired optical clarity, glare, isolation of a transparent
conducting film from a substrate, and reduced manufacturing cost
with little or no trade off. Optical film 600 can be made by first
creating a diffuse surface 604 in substrate 601. Next, barrier film
602 is substantially conformally deposited onto substrate 601 so
that top surface 605 of barrier film 602 is also roughened or
textured. Surfaces 604 and 605 can be similar to one another in
texture and level of roughness.
Alternatively, diffuse properties of surfaces 604 and 605 may be
different. Transparent conductive film 603 is then substantially
conformally deposited onto barrier film 602 so that top surface 606
of transparent conductive film 603 is also roughened or textured.
Surfaces 604, 605, and 606 can be similar in texture and level of
roughness. Alternatively, these surfaces can be different in
texture and/or degree of roughness.
Optical film 600 is particularly suitable, for example, where it is
advantageous to create a diffuse surface in the transparent
conducting film by first generating a rough surface in a substrate
and subsequently coating the substrate with a barrier layer and a
transparent conducting film in such a manner that the roughness in
the substrate, at least to some degree, duplicates in the coated
layers. For example, in some applications it may be difficult or
less advantageous to directly create a rough surface in the
transparent conducting film 606. In such cases, such rough surface
can be generated indirectly by creating a rough surface in a
substrate and replicating the rough surface by conformally coating
the other layers onto the substrate.
It will be appreciated from FIG. 6 that, alternatively, surface 604
of substrate 601 may be substantially smooth. In this case, a rough
surface can be created directly in barrier film 602, and replicated
into transparent conductive film 603 by substantially conformally
coating transparent conductive film 603 onto barrier film 602.
Barrier film 602 reduces or eliminates undesired interaction
between substrate 601 and transparent conductive film 603. For
example, barrier film 602 can reduce or eliminate migration of
impurities. Alternatively, barrier film 602 can reduce or eliminate
chemical reaction. In general, barrier film 602 isolates
transparent conductive film 603 from substrate 601. The isolation
eliminates or reduces an undesired interaction that would, in the
absence of the barrier film, affect the performance of the
substrate and/or the transparent conducting film.
APCVD can be used to manufacture the multilayer optical film 600.
For example, a glass substrate 601, such as a float glass, can be
manufactured using a conventional glass manufacturing process.
Next, a coating of barrier film 602 is applied to the hot glass
substrate. The coating temperature may exceed 400.degree. C. The
coating may be applied to the glass in a float bath or after it is
removed from the bath. The barrier film conformally coats the glass
such that a textured surface 605 results in the barrier film. Next,
a transparent conducting film 603 is coated onto the barrier film.
The conductive coating may also be applied in the float bath and
the coating temperature may exceed 500.degree. C. APCVD is
particularly advantageous for manufacturing optical film 600
because some or all layers can be manufactured on the same line and
at elevated temperatures. Therefore, manufacturing cost is reduced.
Furthermore, performance of the layers can be improved when
deposited at elevated temperatures.
Alternatively, when advantageous, CVD or a combination of CVD and
APCVD can be used to manufacture optical film 600. For example,
barrier film 602 may be coated onto substrate 601 using APCVD and
transparent conductive film 603 may be coated using CVD. The
coatings can be done on the same manufacturing line. Other suitable
methods can also be used for coating the layers. For example,
transparent conductive film 603 can be a transparent organic
conductor. In this case, the organic conductor can be coated onto
barrier film 602 using knife coating, screen printing, inkjet
printing, or any other suitable coating method.
Substrate 601 may be rigid or flexible. The substrate may be
polymeric or any type of glass. For example, the substrate may be
float glass, or it may be made of organic materials such as
polycarbonate, acrylate, and the like. Barrier film 602 may be
silicon dioxide or tin oxide. Transparent conducting film may be a
semiconductor, doped semiconductor, semi-metal, metal oxide, an
organic conductor, a conductive polymer, and the like. Exemplary
inorganic materials include transparent conductive oxides, for
example (ITO), fluorine doped tin oxide, (ATO), and the like.
Exemplary organic materials include conductive organic metallic
compounds as well as conductive polymers such as polypyrrole,
polyaniline, polyacetylene, and polythiophene, such as those
disclosed in European Patent Publication EP-1-172-831-A2.
FIG. 7 illustrates a schematic cross-section of a display system
700 in accordance with one aspect of the present invention. Display
system 700 includes a display 701 and a touch sensor 702. Touch
sensor 702 includes an optical film according to an embodiment of
the present invention. For example, touch sensor 702 can include
optical film 100 of FIG. 1, optical film 300 of FIG. 3, optical
film 600 of FIG. 6, optical films of FIGS. 8A 8D, or any other
optical film in accordance with the present invention. Display 701
can include permanent or replaceable graphics (for example,
pictures, maps, icons, and the like) as well as electronic displays
such as liquid crystal displays, cathode ray tubes, plasma
displays, electroluminescent displays, organic electroluminescent
displays, electrophoretic displays, and the like. It will be
appreciated that although in FIG. 7 display 701 and touch sensor
702 are shown as two separate components, the two can be integrated
into a single unit.
All patents, patent applications, and other publications cited
above are incorporated by reference into this document as if
reproduced in full. While specific examples of the invention are
described in detail above to facilitate explanation of, various
aspects of the invention, it should be understood that the
intention is not to limit the invention to the specifics of the
examples. Rather, the intention is to cover all modifications,
embodiments, and alternatives falling within the spirit and scope
of the invention as defined by the appended claims.
* * * * *